1. Field of the Invention
This invention relates in general to improvements in the field of computer systems having backup/restore or archive/retrieve subsystems, and more particularly, to storage-controller-managed outboard incremental backup/restore of data.
2. Description of Related Art
In a data processing system, a backup/restore subsystem is typically used to save a recent copy or version of a file or portion thereof on some form of backup data storage device, such as magnetic or optical disk drives, tape drives, or other memory. The backup/restore subsystem is used to protect against loss of data. For example, if an on-line version of a file is destroyed, corrupted, deleted, or changed because of power failure, hardware, or software error, user error or some other type of problem, the latest version of that file which is stored in a backup/restore subsystem can be restored and therefore the risk of loss of data is minimized. It is readily apparent that backup/restore subsystems are and will remain an important part of the field of data processing.
At the present time, the majority of backup/restore subsystems are executed by host computers and manage the backup/restore functions for one or more data storage devices connected thereto. Typically, a backup operation is performed on a predetermined schedule such as once each day, week, month, or each time that a file has been updated and saved.
Backup/restore subsystems typically utilize the full backup method and/or the incremental backup method to enable the storage of and retrieval of multiple versions of a given file. The full backup method backs up an entire collection of files, or a file system, regardless of whether individual files in that collection have been updated or not. Often, multiple full versions of each file are maintained on a storage device in the full backup method. The incremental backup method is an alternative to the full backup method where only those files, in any given collection of files, which have been changed since the previous incremental or full backup are backed up.
Backup/restore subsystems generally consume a large part of the processing power of a host computer and the data storage devices attached thereto because of the large amounts of data being accessed. Those engaged in the field of data processing and especially in the field of backup/restore subsystems are continuously striving to find improved methods and systems to reduce the demands of backup/restore subsystems.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method, apparatus, and article of manufacture for a storage-controller-managed outboard incremental backup/restore of data. An indicator is assigned to an associated portion of data stored in a data storage device, wherein the indicator resides in a memory of a storage controller coupled to the data storage device. A value of the indicator residing within the memory of the storage controller is set when the associated portion of the data has changed. The associated portion of the data stored in the data storage device is backed using the storage controller when the value of the indicator residing within the memory of the storage controller is set. The value of the indicator residing within the memory of the storage controller is cleared when the associated portion of the data has been backed up.
An object of the present invention is to provide for storage controller management of backup/restore operations. Another object is to provide for continuous, outboard incremental backup of data. Yet another object is to reduce the overhead on the host computer of performing backup/restore operations on attached data storage devices. A further object is to provide more reliable backup/restore methods.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.